1. Field of the Invention
The present invention relates generally to spinners and fans blades for gas turbine engine fan assemblies and, more specifically, to spinners with fairings or bumps directly upstream of fan blades.
2. Description of Related Art
Aircraft turbofan gas turbine engines include a fan assembly having a plurality of circumferentially spaced apart fan blades extending radially outwardly from a rotor disk. Ambient airflow is channeled between the blades and pressurized thereby for generating thrust for powering the aircraft in flight. The fan assembly typically includes a plurality of circumferentially spaced apart fan blades each having a dovetail root disposed in a complementary, axially extending dovetail groove or slot in a perimeter or rim of a rotor disk or drum. A spinner is mounted to a front end of the fan assembly to provide smooth airflow into the fan as illustrated in U.S. Pat. No. 6,416,280, by Forrester et al., entitled “One Piece Spinner”, which issued Jul. 9, 2002, and which is incorporated herein by reference.
Some spinners are one piece spinners that attach directly to the disk post and some spinners are two piece spinners that have an upper portion of the spinner attached to a flange extending axially forwardly from a disk and a lower portion of the spinner attached to the upper portion of the spinner. This upper portion of the spinner is referred to as a spinner support.
A spinner support 1, similar to what is found in the prior art, is illustrated in FIGS. 1 and 2 and includes circumferentially spaced apart aerodynamic fairings 2 located along an aft portion 4 of the spinner support 1. The aerodynamic fairings 2 are designed to cover and shield radial portions of leading edges of each of fan blades in a fan of an engine (see FIGS. 3-5). Such fairings have also been referred to as bumps. These fairings have been used in aircraft gas turbine engines, for example in the GE-90 115B.
Adding this 3D feature, aerodynamic fairing 2 or bump to the conical surface 9 of the spinner support 1 (or to a one piece spinner) forward of the fan blade allows the fan blade profile to be streamlined and be made more aerodynamic without changing the blade shank. The fairing portion guides the airflow to either side of the blade lead edge profile at the blade root. The circumferentially spaced apart fairings or bumps are formed or machined on the spinner or spinner support 1.
In order to make engines more efficient, there are efforts to increase the fan blade radius ratio (RR) which is a ratio of inner fan flowpath diameter/outer flowpath diameter and which indicates how much airflow can be passed through the engine. A smaller radius ratio (RR) results in a larger flow area, and better performance. As the fan blade radius ratios decrease by lowering the fan platform flowpath surface, the fan blade leading edge profile begins to become larger and abrupt. RR may be decreased by increasing the outer fan diameter or making the inner flowpath and inner flowpath diameter smaller which is preferred. Increasing the overall fan diameter is less desirable because it increases drag.
Maximizing a low radius ratio design results in the blade LE profile being more exposed to the aerodynamic flow path. This LE needs to be protected resulting in a fairing shape that is larger in order to provide aerodynamic smoothness. This, in turn, results in a complex machined spinner or spinner support with large 3D aerodynamic fairings or bumps directly upstream of the fan blades.
It is highly desirable to avoid expensive and complex machining of the spinner or spinner support in order to provide larger 3D aerodynamic fairings or bumps directly upstream of the fan blades.